Low-Intensity Transcranial Ultrasound Stimulation Modulates the Excitability of Motor Cortical Neural Activity by Stimulating the Cerebellum.

Functional connectivity between the cerebellum and the motor cortex is critical for motor function. Low-intensity transcranial ultrasound stimulation (TUS) has been proved to directly activate cerebellar neural activity. However, whether and how TUS of the cerebellum modulates neural activity in the motor cortex is unclear. In the study, TUS with different parameters was used to stimulate the mouse cerebellar region while local field potentials (LFP) in the cerebellum and the motor cortex were simultaneously recorded, as well as neuronal calcium ion activity. We discovered that: 1) TUS can increase the amplitude and power intensity of LFP in the cerebellum and motor cortex, which linearly increasing with the increase of ultrasound intensity, and nonlinearly increasing with the increase of the duty cycle; 2) TUS in the cerebellum significantly increased the firing time and peak of neurons of the motor cortex, which also increased linearly with the increase of ultrasound intensity and nonlinearly with the increase of duty cycle; 3) The cross-correlation information of the LFP between the cerebellum and motor cortex was enhanced, which depends on ultrasound intensity and duty cycle; 4) TUS in the cerebellum for 7 days improved the motor ability of ischemic stroke mice. Taken together, the above findings indicate that TUS of the cerebellum can modulate the excitability of neural activity in the motor cortex, which is important in modulating the symptoms of motor cortex-related diseases. We also describe the ameliorative effect of TUS of the cerebellum on movement disorders caused by cerebral ischemia.